An input detection device capable of detecting proximity or contact of an external object, so-called a touch panel, has been known. Such a touch panel can be used in combination with a display device in which liquid crystal, an OLED, or the like are used and can be mounted on electronic equipment such as a mobile phone or a tablet.
A capacitive sensing touch panel has been known as an example of the input detection device which detects an external object such as a finger. In addition, a touch panel capable of detecting a pen such as a stylus, as an external object, also has been known. With a pen, a region smaller than a region that can be designated with a finger can be designated, and a handwritten character can be input. An electromagnetic induction touch panel has been known as an example of the method for detecting touch with a pen.
A technique related to the electromagnetic induction touch panel is described, for example, in Japanese Patent Application Laid-Open Publication No. H10-49301 (Patent Document 1).